1. The Field of the Invention
The present invention relates generally to optoelectronic devices. More specifically, the present invention relates to monolithic single and dual detector structures for use with optoelectronic devices.
2. The Relevant Technology
Computing, telecom and networking technology have transformed our world. As the amount of information communicated over networks has increased, high speed transmission has become ever more critical. Many high speed data transmission networks rely on optical transceivers and similar devices for facilitating transmission and reception of digital data embodied in the form of optical signals over optical fibers. Optical networks are thus found in a wide variety of high speed applications ranging from modest Local Area Networks (“LANs”) to backbones that define a large portion of the infrastructure of the Internet.
Typically, data transmission in such networks is implemented by way of an optical light source, such as a laser or Light Emitting Diode (“LED”). The optical light source emits light when current is passed through it, the intensity of the emitted light being a function of the magnitude of the current. Data reception is generally implemented by way of an optical receiver (also referred to as an optoelectronic transducer), an example of which is a photodiode. The optoelectronic transducer receives light and generates a current, the magnitude of the generated current being a function of the intensity of the received light.
In certain optical network applications, such as dense wavelength division multiplexing (“DWDM”) networks, it may be desirable to monitor the optical output power and/or wavelength of light signals emitted by the optical light source. If the output power and/or emission wavelength are above or below a desired power and/or wavelength, a feedback loop can then be used to increase or decrease the appropriate parameter.
In a conventional monitoring arrangement used with edge emitting optical light sources (e.g., distributed feedback lasers, and the like), a power monitor photodiode is placed behind the back facet of the edge emitter. Although most of the light emitted by the edge emitter escapes through the front facet of the edge emitter, a proportional amount of light also escapes through the back facet. Some of the light emitted through the back facet is then absorbed by the power monitor photodiode, generating a current in the power monitor photodiode that is proportional to the absorbed light. The magnitude of the photocurrent generated by the power monitor photodiode can be used to measure the optical output power of the edge emitter.
The wavelength of the light emitted by the edge emitter can be measured using a beam splitter, a second monitor photodiode, and a narrow bandpass wavelength filter. The beam splitter is typically placed in front of the front facet of the edge emitter, allowing most of the light emitted by the edge emitter to pass through, while redirecting a proportional amount of the emitted light through the wavelength filter to the second monitor photodiode.
Similar to the power monitor photodiode, the second monitor photodiode generates a current proportional to the light absorbed by the second monitor photodiode. However, the amount of light that reaches the second monitor photodiode through the wavelength filter depends on both the initial optical output power (which can be measured by the power monitor photodiode) and the wavelength of the emitted light. The closer the emission wavelength is to the bandpass of the wavelength filter, the greater the amount of light that passes through the wavelength filter to the second monitor photodiode. Consequently, a ratio of the currents generated by the power monitor photodiode and the second monitor photodiode can be used to determine the wavelength of the light emitted by the edge emitter. In many cases, this determination is accomplished by looking up the ratio in a lookup table or calibration file.
Although beneficial for power and wavelength monitoring and control, conventional monitoring devices suffer from a number of disadvantages. First, conventional monitoring devices involve numerous discrete optical components that require significant real estate in an optical light source package. Additionally, the cost of the discrete optical components required for monitoring power and/or wavelength increases the material cost of optical light source packages in which they used. Moreover, the difficulties in properly aligning the discrete optical components increase the complexity and cost of manufacturing the optical light source packages that include such components.
The subject matter claimed herein is not limited to embodiments that solve any disadvantages or that operate only in environments such as those described above. Rather, this background is only provided to illustrate one exemplary technology area where some embodiments described herein may be practiced